The disclosure of Japanese Patent Application Nos. 11-357750 filed on Dec. 16, 2000 and 2000-33729 filed on Feb. 10, 2000 including the specification, drawings and abstract are incorporated herein by reference in their entirety.
1. Field of the Invention
The invention generally relates to a vehicle deceleration control apparatus that adds deceleration to a vehicle, and a control method thereof. In particular, the invention relates to a vehicle deceleration control apparatus that adds deceleration to a vehicle according to an accelerator operation state, and a control method thereof.
2. Description of the Related Art
A deceleration control apparatus that adding deceleration to a vehicle by applying braking force when the driver releases an accelerator pedal is known as related art of the invention. Japanese Laid-Open Publication No. HEI 9-95222 discloses a deceleration control apparatus that adds braking force to a main brake system when an accelerator pedal is in a deceleration range.
Provision of such a deceleration control apparatus to a vehicle eliminates the need to operate a brake pedal frequently upon gently accelerating/decelerating the vehicle. As a result, deceleration response is improved, so that easy drive can be realized.
However, in the deceleration control apparatus of the related art, unintended deceleration is generated due to the driver""s unconscious operation of an accelerator. Therefore, the driver may possibly feel uncomfortable, degrading the driving feeling. The above-mentioned publication discloses that a switch that enables the driver to turn on/off the deceleration control apparatus is provided to overcome such a problem. However, such a selective switch makes the operation troublesome to the driver. Moreover, if the driver wrongly selects or neglects to select, deceleration is generated or is not generated contrary to the driver""s intention, so that the driving feeling may rather be degraded.
In view of the foregoing problems, it is an object of the invention to provide a vehicle deceleration control apparatus capable of generating assist deceleration that is less uncomfortable to the driver.
In order to achieve the above-mentioned object, a vehicle deceleration control apparatus according to an aspect of the invention includes determining device that determines an accelerator operation state of a driver, deceleration adding device that adds deceleration to a vehicle, and a control device that controls the deceleration adding device so as to add the deceleration when the determining device determines that the accelerator operation state is a predetermined accelerator operation state. The vehicle deceleration control apparatus further includes an operation element capable of being operated by the driver, and provided to change an operating state of a vehicle movement controller other than the deceleration adding device. The control device changes an operating state of the It deceleration adding device according to an operation state of the operation element.
According to the invention, in the vehicle deceleration control apparatus that adds assist deceleration by the deceleration adding device when the accelerator operation state is a predetermined accelerator operation state, an operating state of the deceleration adding device is changed according to an operation state of the operation element (e.g., a switch or lever for changing an operating state of a driving system) that is capable of being operated by the driver and provided to change an operating state of the vehicle movement controller other than the deceleration adding device. Thus, addition of the deceleration can be adjusted according to a current operating property of the vehicle, thereby allowing addition of the deceleration that is comfortable to the driver.
For example, the operation element is a changing device that changes an operating state of an automatic transmission. In this case, the deceleration is actively added in a shift position where the driver intends to actively apply engine brake. On the other hand, the deceleration to be added is suppressed in a shift position where the driver does not intend to use the engine brake. Thus, the assist deceleration that is less uncomfortable to the driver can be added.
The changing device may either be shift-range selecting device, or shift-mode changing device that selectively changes a shift mode between an auto-shift mode in which gearshift is automatically conducted according to a running state of the vehicle and a manual shift mode in which gearshift to a corresponding gear is conducted according to an operation state of a gearshift operation member by the driver. By adjusting the assist deceleration according to the shift mode as switched by the driver, addition of the assist deceleration can be conducted further as intended by the driver.
The control device may limit the deceleration to be added by the deceleration adding device, in a case where the operation element is in a predetermined operation state. For example, in a case where the shift-mode changing device is in the auto-shift mode, the control device preferably limits the deceleration to be added by the deceleration adding device as compared to a case where the shift-mode changing device is in the manual shift mode. The control device may inhibit addition of the deceleration by the deceleration adding device in a case where the shift-mode changing device is in the auto-shift mode, and may control the deceleration adding device so as to add the deceleration to the vehicle in a case where the shift-mode changing device is in the manual shift mode.
Alternatively, the control device may adjust a rate of change with time in the deceleration to be added by the deceleration adding device, according to the operation state of the operation element. Even if the deceleration generated after a predetermined time is the same, application of the deceleration can be conducted as intended by the driver by changing a way to apply the deceleration.
Alternatively, the vehicle deceleration control apparatus according to the invention may start adding the deceleration a predetermined delay time after the accelerator operation state becomes a predetermined accelerator operation state. This delay time may be set based on variation in the accelerator operation state.
The driver tends to operate the accelerator unconsciously. The inventor found that the larger the variation with time in driver""s accelerator operation is, the more frequently the accelerator is rendered in a predetermined operation state (i.e., the state in which the deceleration is applied) for a short time, whereby unintended deceleration is generated, degrading the driving feeling. Therefore, according to the invention, in the case of the driver having large variation with time in accelerator operation, a delay time is provided which is longer than the time period during which the accelerator may be rendered in the predetermined operation state due to the driver""s unconscious operation. Thus, the deceleration is added after the delay time, so that generation of unintended deceleration is controlled.
It is preferable that the delay time be set to a larger value as a frequency at which the accelerator operation state varies is higher. Alternatively, the delay time may be set to a larger value as a frequency at which the accelerator operation state is determined to be the predetermined operation state is higher. It can be determined that, as the frequency at which the accelerator operation state varies is higher, and as the frequency at which the accelerator operation state is determined to be the predetermined operation state is higher, the driver has larger variation with time in his/her unconscious accelerator operation. Therefore, it is preferable to increase the delay time in the case of such a driver.
In addition, a vehicle provided with the vehicle deceleration control apparatus according to the invention may have an automatic transmission having a plurality of shift patterns, and the control device may change an operating state of the deceleration adding device according to a current shift pattern of the automatic transmission. By adjusting the applied deceleration according to the shift pattern, the assist deceleration can be applied as intended by the driver.
This deceleration adding device preferably adds the deceleration by controlling braking force. In a case where a mechanism for assisting the brake operating capability with the braking force is used, the invention can be implemented only with simple modification.
The aspect of the invention is not limited to such a vehicle deceleration control apparatus as described above. Another aspect of the invention is, e.g., a vehicle provided with a vehicle deceleration control apparatus, and a method for controlling a vehicle deceleration control apparatus.